Ribbed film structures with voiding agent created visual characteristics

ABSTRACT

In one example embodiment, a film includes a coextruded structure having both an extruded ribbed skin layer that includes a plurality of ribs, and a core layer. The ribs are spaced apart by a web that is integral with the ribs. The film also includes a voiding agent in the ribs of the skin layer.

RELATED APPLICATIONS

This application is related to the following United States patentapplications filed the same day herewith: RIBBED FILM STRUCTURES WITHPIGMENT CREATED VISUAL CHARACTERISTICS, Docket No. 492.1116; and,DISCONTINUOUSLY LAMINATED FILM STRUCTURES WITH IMPROVED VISUALCHARACTERISTICS, Docket No. 492.1120. As well, this application is acontinuation-in-part (CIP) of, and claims priority to, U.S. patentapplication Ser. No. 13/454,412, filed Apr. 24, 2012, entitledTHERMOPLASTIC FILMS WITH VISUALLY-DISTINCT STRETCHED REGIONS AND METHODSFOR MAKING THE SAME, which claims priority to U.S. Patent ProvisionalApplication Ser. No. 61/478,639, filed Apr. 25, 2011, entitledTHERMOPLASTIC FILMS WITH VISUALLY-DISTINCT STRETCHED REGIONS AND METHODSFOR MAKING THE SAME. The present application also is acontinuation-in-part (CIP) of, and claims priority to, U.S. patentapplication Ser. No. 13/454,474, filed Apr. 24, 2012, entitledMULTI-LAYER FILMS WITH VISUALLY-DISTINCT REGIONS AND METHODS OF MAKINGTHE SAME, which claims priority to U.S. Patent Provisional ApplicationSer. No. 61/478,643, filed Apr. 25, 2011, entitled MULTI-LAYER FILMSWITH VISUALLY-DISTINCT REGIONS AND METHODS OF MAKING THE SAME. Thepresent application also is a continuation-in-part (CIP) of, and claimspriority to, U.S. patent application Ser. No. 13/552,352, filed Jul. 18,2012, entitled MULTI-PLY PUCKERED FILMS FORMED BY DISCONTINUOUSLAMINATION OF FILMS HAVING DIFFERENT REBOUND RATIOS, and is acontinuation-in-part (CIP) of, and claims priority to, U.S. patentapplication Ser. No. 13/660,844, filed Oct. 25, 2012, entitledTHERMOPLASTIC MULTI-PLY FILM WITH METALLIC APPEARANCE, and is acontinuation-in-part (CIP) of, and claims priority to, U.S. patentapplication Ser. No. 12/947,025, filed Nov. 16, 2010, entitledDISCONTINUOUSLY LAMINATED FILM. All of the aforementioned applicationsare incorporated herein in their respective entireties by thisreference.

BACKGROUND

As the costs of resin materials increase along with desires to minimizethe impact of resin material waste, manufacturers are moving toward useof thinner and thinner gauges of resin films in their products. This isparticularly true of manufacturers that implement high volumes of resinfilms in various forms, such as resin films for use in storage and wasteproducts. While thinner gauge materials can represent obvious costsavings to the manufacturer, conventional production mechanisms can meanthat use of thinner gauge film precursors results in lower durability ofthe end product. Although some recent technology may result, in somecases at least, in relatively thinner gauge products that may be asstrong as their thicker counterparts, customers naturally sense fromprior experience that thinner gauge materials are lower in quality anddurability.

One instant cue to a customer of lower quality and durability of a bagis not only how thick or thin the bag feels, but also how thin or weakthe bag “looks.” Generally speaking, customers tend to view translucenceas an indication of relatively low strength. Thus, despite the fact thatsome conventional mechanisms can improve some aspects of film strengthwhile nevertheless using thinner gauge film materials, the translucenceof such bags tends to cause customers to believe the bag is neverthelesslow quality. Manufacturers may try to overcome these sorts ofdifficulties by adding colorants or voiding agents to minimize thisissue.

Depending on how they are used, however, colorants and voiding agentscan sometimes weaken the chemical bonds in the film, and create a stillweaker film. Moreover, the use of certain colors in a film or filmstructure may present unique challenges. For example, films with a whitecolor may employ a pigment such as titanium dioxide (TiO2). However,titanium dioxide is quite expensive and may significantly increase thecost of a film that employs such a pigment. Other conventionalmechanisms involve using multiple, very low gauge films in a laminatestructure, where at least one of the films is colored. However, theaforementioned types of color additions to film, and the types of filmstructures are not typically well-suited for some applications and/orhave proven to be problematic for various reasons in addition to thosenoted above.

For example, one color changeable laminate structure (or “laminate”)includes a pair of films in intimate contact with each other, andfurther includes a color generating film positioned adjacent one of thefilms. So long as the films are in intimate contact with each other, thelaminate generates an interference color. However, absent intimatecontact between the films, no color is generated. Thus, the colorchangeable laminate may not be well-suited for use in environmentswhere, for example, delamination of the films is possible. As well,production processes for this structure can be difficult, and in somecases must be strictly controlled to ensure intimate contact throughoutthe entirety of the laminated films.

Another laminate displays a color change when the laminate is bent. Thisis achieved with a color generating metal disposed on a film of thelaminate. The metal is in intimate contact with an anodic film, andcreates color by light interference absorption effects. Absent intimatecontact between the metal and the anodic film however, the colorgeneration effects are not achieved. Moreover, production processes canbe difficult, and in some cases must be strictly controlled to ensureintimate contact between all portions of the metal and the anodic film.As well, this laminate may not be well-suited for environments where:the use of metal is undesirable or impractical; delamination of themetal and anodic film is possible; and/or, it is desired to maintain thecolor of the laminate notwithstanding temporary or permanent changes tothe geometry of the laminate.

As a final example, a further laminate structure can be constructed todisplay an irreversible color change upon delamination of two films inintimate contact with each other. Absent intimate initial contactbetween the films however, the color generation effects are notachieved. Thus, production processes must be strictly controlled toensure intimate contact between the films so that when the films aredelaminated, the desired effect is achieved. As well, this laminate maynot be well-suited for environments where it is desired to maintain thecolor of the laminate notwithstanding temporary or permanent changes tothe geometry of the laminate. Finally, this laminate structure maynecessitate user intervention to effect the delamination necessary forachievement of the irreversible color change.

As the foregoing discussion suggests, there is a need for quality endproducts that, notwithstanding other aspects of their appearance and/ortactile impression, are configured to provide a positive indication tothe consumer as to the quality of those products.

BRIEF SUMMARY OF AN EXAMPLE EMBODIMENT

One or more embodiments within the scope of the invention may beeffective in overcoming one or more disadvantages in the art. In oneexample embodiment, a film includes a coextruded structure having bothan extruded ribbed skin layer that includes a plurality of ribs, and acore layer. The ribs are spaced apart by a web that is integral with theribs. The film also includes a voiding agent that is substantially moreapparent in the ribs than in the web, such that a contrast in colorand/or color intensity between the ribs and the web is visible.

The foregoing embodiment is provided solely by way of example and is notintended to limit the scope of the invention in any way. Consistently,various other embodiments of an extruded, multi-layer film having aribbed outer layer, discontinuously laminated film structures, andassociated production processes, within the scope of the invention aredisclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings contain figures of example embodiments to furtherillustrate and clarify various aspects of the present invention. It willbe appreciated that these drawings depict only example embodiments ofthe invention and are not intended to limit its scope in any way.Aspects of the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 discloses aspects of an extrusion die such as may be employed toform an extruded, ribbed film layer;

FIG. 2 a discloses aspects of an MD machine and associated MD rollingprocess;

FIG. 2 b is a detail view of the MD machine of FIG. 1, and disclosesaspects of the operation of the MD machine relative to a film;

FIG. 2 c is another detail view illustrating the formation of indicia ona portion of a film, a rib in this case, by a tool such as a ringroller;

FIG. 2 d discloses some example cross-sectional rib shapes andarrangements;

FIG. 3 discloses aspects of an example process for producing an extrudedmultilayer film;

FIGS. 4 a-1 and 4 a-2 depict a first example of a film, referred toherein as Film ‘A’, where the film in FIGS. 4 a-1 and 4 a-2 is anun-stretched film;

FIGS. 4 b-1 and 4 b-2 depict a first variation of Film ‘A,’ where thefilm has been ring rolled in the machine direction;

FIGS. 4 c-1 and 4 c-2 disclose another depiction of the first variationof Film ‘A,’ where the film has been ring rolled in the machinedirection;

FIGS. 4 d-1 and 4 d-2 depict of a second variation of Film ‘A,’ wherethe film has been ring rolled first in the machine direction, andsubsequently in the transverse direction;

FIGS. 5 a-1 and 5 a-2 depict a second example of a film, referred toherein as Film ‘B’, where the film in FIGS. 5 a-1 and 5 a-2 is anun-stretched film;

FIGS. 5 b-1 and 5 b-2 depict a first variation of Film ‘B,’ where thefilm has been ring rolled in the machine direction;

FIGS. 5 c-1 and 5 c-2 depict a second variation of Film ‘B,’ where thefilm has been ring rolled first in the machine direction, andsubsequently in the transverse direction;

FIGS. 6 a-1 and 6 a-2 depict a third example of a film, referred toherein as Film ‘C,’ where the film in FIGS. 6 a-1 and 6 a-2 is anun-stretched film;

FIGS. 6 b-1 and 6 b-2 depict a first variation of Film ‘C,’ where thefilm has been ring-rolled in the machine direction;

FIGS. 6 c-1 and 6 c-2 depict a second variation of Film ‘C,’ where thefilm has been ring rolled first in the machine direction, andsubsequently in the transverse direction;

FIGS. 7 a-1 and 7 a-2 depict a fourth example of a film, referred toherein as Film ‘H,’ where the film in FIGS. 7 a-1 and 7 a-2 is anun-stretched film;

FIGS. 7 b-1 and 7 b-2 depict a first variation of Film ‘H,’ where thefilm has been ring rolled in the machine direction; and

FIGS. 7 c-1 and 7 c-2 depict a second variation of Film ‘H,’ where thefilm has first been ring rolled in the machine direction, andsubsequently in the transverse direction.

DETAILED DESCRIPTION

Example embodiments of the invention generally concern extruded films.More particularly, at least some embodiments are directed to extrudedfilms with one or more visual and/or tactile elements perceptible by auser, while other embodiments are directed to methods for producing suchfilms. Insofar as such films may, subsequent to their formation, beemployed in the construction of structures such as discontinuouslylaminated film structures, such films may be referred to herein asprecursor films. The films disclosed herein may be employed in a varietyof different end products, examples of which include, but are notlimited to, grocery bags, trash bags, sacks, yard waste bags, packagingmaterials, feminine hygiene products, baby diapers, adult incontinenceproducts, sanitary napkins, bandages, food storage bags, food storagecontainers, thermal heat wraps, facial masks, wipes, and hard surfacecleaners.

A. Aspects of Various Example Embodiments

It should be noted that the embodiments disclosed herein do notconstitute an exhaustive summary of all possible embodiments, nor doesthe following discussion constitute an exhaustive list of all aspects ofany particular embodiment(s). Rather, the following discussion simplypresents selected aspects of some example embodiments. It shouldlikewise be noted that nothing herein should be construed asconstituting an essential or indispensable element of any invention orembodiment. Rather, and as the person of ordinary skill in the art willreadily appreciate, various aspects of the disclosed embodiments may becombined in a variety of ways so as to define yet further embodiments.Such further embodiments are considered as being within the scope ofthis disclosure. As well, none of the embodiments embraced within thescope of this disclosure should be construed as necessarily resolving,or being limited to the resolution of, any particular problem(s). Norshould such embodiments be construed to necessarily implement, or belimited to implementation of, any particular effect(s).

Films within the scope of this disclosure may possess or exhibit avariety of different physical, visual, and/or optical characteristics.The visual and/or optical characteristics may be achieved without theuse, for example, of metal layers, color generating laminates,delamination, and/or bending of the film structures.

Illustrative examples of effects such as visual appearances that may bemanifest in various embodiments of a film include: a coextruded filmwith a plurality of layers, including a ribbed outer layer, where acontrast in color and/or color intensity is apparent between the ribsand the webs between the ribs; a film with a ribbed outer layer thatincludes a voiding agent; a film with a ribbed outer layer that includesa stress-sensitive voiding agent; a film with a ribbed outer layerlacking a coloring agent, and an inner layer lacking a coloring agent; afilm with an outer layer having white ribs and colorless webs, and aninner layer lacking a coloring agent; a film with an outer layer havingblack ribs and colorless webs, and an inner layer lacking a coloringagent; a film with an outer layer having white ribs and black webs, anda black inner layer; and, a coextruded film with an outer layer havingblack ribs and white webs, and further including a white inner layer.

It should be noted that the aforementioned rib, web, and layer colorsare provided by way of example. Thus, for example, the inner layer andouter layer need not be black, or white, but may include any coloringagent and/or voiding agent capable of imparting or causing theappearance of any other color. In general, any color(s) may be used thatprovide a visual contrast between the ribs and webs of a ribbed layer.

As suggested by the foregoing general considerations, films andassociated products within the scope of this disclosure may include oneor more of the following, in any suitable combination: a core layer witha coloring agent; an core layer lacking a coloring agent; a skin layerthat includes a voiding agent; an skin layer lacking a coloring agent; aribbed skin layer; a ribbed skin layer containing a voiding agent; aribbed skin layer containing a stress-sensitive voiding agent; a ribbedskin layer including a coloring agent; an ribbed skin layer lacking acoloring agent; two or more coextruded layers, where one of the layersis a core layer, and one of the layers is a skin layer; two or morecoextruded layers, where one of the layers is a core layer, and one ofthe layers is a ribbed skin layer having ribs whose color contrasts witha color of webs between the ribs; three or more coextruded layers,wherein two of the layers are skin layers and one of the layers is acore layer positioned between the skin layers; two or more coextrudedlayers, where one of the layers is a core layer, and one of the layersis a ribbed skin layer; three or more coextruded layers, wherein two ofthe layers are skin layers, one of the layers is a core layer positionedbetween the skin layers, and one of the skin layers is ribbed; two ormore coextruded layers, where one of the layers is a core layer, and oneof the layers is a skin layer, and the core layer and the skin layerlack a coloring agent; an extruded film with a ribbed skin layerincluding one or more of stitches, discontinuous lines, colored ribs,and, ribs with a metallic appearance; an extruded film with a ribbedskin layer bearing one or more indicia of post-extrusion processing ofthe extruded film; an extruded film with a ribbed skin layer bearing oneor more indicia of post-extrusion ring rolling of the extruded film; anextruded film with a ribbed skin layer including one or more visualand/or tactile elements at least partly resulting from post-extrusionprocessing; an extruded film with a ribbed skin layer including one ormore visual and/or tactile elements at least partly resulting frompost-extrusion processing, the visual and/or tactile elements includingone or more of stitches, discontinuous lines, colored ribs, and, ribswith a metallic appearance; an extruded film with a ribbed skin layerincluding one or more visual and/or tactile elements produced at leastin part by one or both of MD ring rolling and TD ring rolling, and thevisual and/or tactile elements including one or more of stitches,discontinuous lines, colored ribs, and, ribs with a metallic appearance,and, an end product including any of the foregoing layers, orcombinations of those layers.

It will be appreciated from the foregoing, and the other disclosureherein, that a variety of different embodiments may be defined. Someexamples of such embodiments are set forth below. Such embodiments arenot intended to limit the scope of the invention in any way.

In a first example embodiment, an extruded multilayer film includes aribbed skin layer having ribs connected by webs, where the webs and ribsare integral with each other.

In a second example embodiment, an extruded multilayer film includes aribbed skin layer, and a core layer.

In a third example embodiment, an extruded multilayer film includes acore layer and a pair of skin layers, where one or both of the skinlayers are ribbed.

In a fourth example embodiment, an extruded multilayer film includes acore layer, and a ribbed skin layer that includes a voiding agent.

In a fifth example embodiment, an extruded multilayer film includes acore layer that includes a coloring agent, and a ribbed skin layer thatincludes a voiding agent.

In a sixth example embodiment, an extruded multilayer film includes acore layer, and a ribbed skin layer that includes a stress-sensitivevoiding agent.

In a seventh example embodiment, an extruded multilayer film includes acore layer and a ribbed skin layer, where the ribs of the ribbed skinlayer contrast with webs between the ribs in terms of one or both ofcolor, and color intensity.

In an eighth example embodiment, an extruded multilayer film includes acore layer and a ribbed skin layer, where the ribs of the ribbed skinlayer include a voiding agent, and webs between the ribs aresubstantially colorless.

In a ninth example embodiment, an extruded multilayer film includes acore layer and a ribbed skin layer, where the core layer is one ofcolorless or black, and the ribbed skin layer is one of colorless orwhite.

In a tenth example embodiment, an extruded multilayer film including aribbed skin layer bears one or more indicia of post-extrusionprocessing, the one or more indicia being perceptible by one or moresenses of a user.

In an eleventh example embodiment, an extruded multilayer film includinga ribbed skin layer bears one or more indicia of post-extrusionprocessing, where the post-extrusion processing is one or both of MDring rolling, and TD ring rolling.

In a twelfth example embodiment, an extruded multilayer film including aribbed skin layer bears one or more indicia of post-extrusionprocessing, where the indicia are present on the ribs of the ribbed skinlayer.

In a thirteenth example embodiment, an extruded multilayer filmincluding a ribbed skin layer bears one or more indicia ofpost-extrusion processing, and the indicia comprise one or more of avisible deformation of a rib, a color of a rib, and a color of a web.

In a fourteenth example embodiment, an extruded multilayer filmincluding a ribbed skin layer bears one or more indicia ofpost-extrusion processing, where the indicia convey informationconcerning a relative strength of the film.

In a fifteenth example embodiment, an extruded multilayer film includinga ribbed skin layer bears one or more indicia of post-extrusionprocessing, where the indicia indicate the imposition of stress and/orstrain on the ribs of the ribbed skin layer.

In a sixteenth example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer.

In a seventeenth example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, and subjecting the extruded multilayer film topost-extrusion processing including one or both of MD ring rolling andTD ring rolling, performed in any order.

In an eighteenth example embodiment, a process to form an extrudedmultilayer film includes adding a coloring agent to one or both of aribbed outer layer and a core layer, and coextruding the ribbed outerlayer together with the core layer.

In a nineteenth example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, where the ribbed outer layer includes a voiding agent.

In a twentieth example embodiment, a process to form an extrudedmultilayer film includes adding a voiding agent to a ribbed outer layerand adding a coloring agent to a core layer, coextruding the ribbedouter layer together with the core layer, and subjecting the extrudedmultilayer film to post-extrusion processing including one or both of MDring rolling and TD ring rolling, performed in any order.

In a twenty first example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, where the core layer lacks a coloring agent and the ribbedouter layer includes a voiding agent, and subjecting the extrudedmultilayer film to post-extrusion processing including one or both of MDring rolling and TD ring rolling, performed in any order.

In a twenty second example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, and producing one or more indicia in the extrudedmultilayer film by subjecting the extruded multilayer film topost-extrusion processing including one or both of MD ring rolling andTD ring rolling, performed in any order.

In a twenty third example embodiment, a process to form an extrudedmultilayer film includes adding a coloring agent to a core layer,coextruding the ribbed outer layer together with the core layer, andproducing one or more indicia in the extruded multilayer film bysubjecting the extruded multilayer film to post-extrusion processingincluding one or both of MD ring rolling and TD ring rolling, performedin any order.

In a twenty fourth example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, where the ribbed outer layer includes a voiding agent andthe core layer lacks a coloring agent, and producing one or more indiciain the extruded multilayer film by subjecting the extruded multilayerfilm to post-extrusion processing including one or both of MD ringrolling and TD ring rolling, performed in any order.

In twenty fifth example embodiment, a process to form an extrudedmultilayer film includes coextruding a ribbed outer layer together witha core layer, and subjecting the extruded multilayer film topost-extrusion processing including one or both of MD ring rolling andTD ring rolling, performed in any order, and the resulting extrudedmultilayer film exhibits a contrast in color and/or color intensitybetween the ribs and one or both of the webs and the core layer.

In further example embodiments, any of the aforementioned extrudedmultilayer films comprises one or more layers of LLDPE.

In further example embodiments, a discontinuously laminated filmstructure includes any of the aforementioned extruded multilayer films.

In further example embodiments, an end product includes any of theaforementioned extruded multilayer films or discontinuously laminatedfilm structures.

In further example embodiments, any of the aforementioned processes usedin whole or in part to produce an end product that includes any of theaforementioned films and/or discontinuously laminated film structures.

For purposes of this disclosure and claims, the term “rib” embraces aportion of extra resin on a surface of a given precursor film, whichportion is an integral portion of the film, and before any subsequenthot or cold forming process on the film, such as a ring rolling process.The “rib,” e.g., reference 251 in FIG. 2 a of a ribbed film, e.g.,reference 250 in FIG. 2 a, may be formed in accordance withimplementations of the present invention via extrusion of molten resinthrough an appropriate die having one or more sets of grooves forforming corresponding ribs. Similarly, for purposes of this descriptionand claims, a “ribbed film” refers to a film that has been extruded inmolten form with one or more ribs, and therefore comprises the one ormore extruded ribs independent of any other striations or rib-likeformations that may occur via any other hot or cold forming processafter the initial extrusion/formation of the rib(s) of the ribbed film.Such other striations or rib-like formations from subsequent formingprocesses are referred to herein generally as “ripple(s).” See, forexample, reference 258 of FIGS. 2 a and 2 b.

In terms of the physical configuration of a “rib,” the scope of theinvention is not limited to any particular form, size or orientationthereof. In general however, the ribs extend outwardly a distance from asurface of the film. In this structure, a web is defined betweenconsecutive ribs. The ribs may or may not have a generally triangularcross-section, but it will be appreciated that, for example, anextrusion die can be configured to produce a rib having any desiredcross-sectional shape.

B. Extruded Multilayer Films

As contemplated herein, multilayer films and extrusion processes forcreating multilayer films embrace, among other things, coextrusion oftwo or more layers of resin through a heated die. Post-extrusionprocessing of the multilayer films may include, for example, ringrolling on one or both of the machine direction (MD), and the transversedirection (TD) which is generally orthogonal to the MD. As used herein,the term “machine direction” or “MD” refers to the direction along thelength of the film, or in other words, the direction of the film as thefilm is formed during extrusion and/or coating. Likewise, the term“transverse direction” or “TD” refers to the direction across the filmor perpendicular to the machine direction. Further, the term “diagonaldirection” or “DD” refers to the direction that is not aligned witheither the length or the width of the film. Finally, a “coextruded” filmrefers to a film having two or more layers that have been coextrudedwith each other.

C. Example Film Materials

The films disclosed herein may comprise any flexible or pliablematerial, including thermoplastic materials that can be formed or drawninto a film. As described above, at least some films within the scope ofthe invention include a plurality of layers, one or more of which may bethermoplastic. Adjuncts may also be included in the film layers, asdesired. Examples of such adjuncts include slip agents, anti-blockagents, tackifiers, coloring agents such as pigments, dyes, dilutepigments, voiding agents, and combinations of the foregoing adjuncts.

The thermoplastic material of the films of one or more implementationscan include, but are not limited to, thermoplastic polyolefins,including polyethylene, polypropylene, and copolymers thereof. Besidesethylene and propylene, exemplary copolymer olefins include, but are notlimited to, ethylene vinylacetate (EVA), ethylene methyl acrylate (EMA)and ethylene acrylic acid (EAA), or blends of such olefins.

Other examples of polymers suitable for use as films in accordance withthe present invention include elastomeric polymers. Suitable elastomericpolymers may also be biodegradable or environmentally degradable.Suitable elastomeric polymers for the film includepoly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene),poly(ethylene-propylene), poly(styrene-butadiene-styrene),poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene),poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),poly(ethylene-methylacrylate), poly(ethylene-acrylic acid),poly(ethylene butylacrylate), polyurethane,poly(ethylene-propylene-diene), ethylene-propylene rubber, andcombinations of the foregoing.

D. General Aspects of Some Example Production Processes

Consistent with the varied natures of films, various processes, andcombinations thereof, may be used in the production of the filmsdisclosed herein. Examples of such processes include, but are notlimited to, extrusion, heat bonding, ultrasonic bonding, adhesivebonding, incremental stretching, pressure bonding techniques such asmachine direction (MD) ring rolling, transverse direction (TD) ringrolling, diagonal direction (DD) ring rolling, and any ring rollingprocess that results in the formation of a laminated film withstrainable networks. Treatment with a corona discharge may be used toenhance any of the aforementioned methods.

More generally however, any other process(es) that produces multilayerfilms, may be employed, and the scope of the invention is not limited toany particular production process(es).

Consistent with this disclosure, manufacturers may form individual filmsto be coextruded together so as to provide improved strengthcharacteristics using a wide variety of techniques. For example, amanufacturer can form a precursor mix of the thermoplastic materialincluding any optional additives. The manufacturer can then form thefilm(s) from the precursor mix using conventional flat extrusion, castextrusion, or coextrusion to produce monolayer, coextruded bilayer, ormultilayered films. Alternative to conventional flat extrusion or castextrusion processes, a manufacturer can form the films using othersuitable processes, such as, a blown film process to produce monolayer,bilayer, or multilayered films, which are subsequently discontinuouslylaminated with another film layer at a later stage. If desired for agiven end use, the manufacturer can orient the films by trapped bubble,tenterframe, or other suitable processes. Additionally, the manufacturercan optionally anneal the films.

Where extrusion is employed, a manufacturer can use multiple extrudersto supply different melt streams, which a feed block can order intodifferent channels of a multi-channel die. The multiple extruders canallow a manufacturer to form a multi-layered film with layers havingdifferent compositions. Such multi-layer film may later bediscontinuously laminated with another layer of film, which may or maynot be multi-layer itself, to provide a discontinuously laminated filmstructure.

In a blown film process, the die can be an upright cylinder with acircular opening, and the die may include geometric features about itsinner surface that can form various structures on the film as the moltenplastic is extruded through the die. As disclosed elsewhere herein, oneexample of such a geometric feature is a set of teeth disposed about theinner surface of the die which may cause the formation of ribs on thefilm as the molten plastic is passed through the die. One example ofsuch a die is disclosed in FIG. 1 and discussed in more detail below.

With continuing reference to the blown film process, rollers can pullmolten plastic upward away from the die. An air-ring can cool the filmas the film travels upwards. An air outlet can force compressed air intothe center of the extruded circular profile, creating a bubble. The aircan expand the extruded circular cross section by a multiple of the diediameter. This ratio may be referred to as the “blow-up ratio,” or BUR.When using a blown film process, the manufacturer can collapse the filmto double the plies of the film. Alternatively, the manufacturer can cutand fold the film, or cut and leave the film unfolded.

A more detailed discussion of various specific examples of productionprocesses that may be used in the production of the films disclosedherein is set forth elsewhere herein.

E. Example Production Equipment

Directing attention first to FIG. 1, details are provided concerningaspects of a machine 50 that may be used to form coextruded multilayerfilms such as those disclosed herein. As the general aspects of theoperation of such a machine and its operation have been set forthelsewhere herein, the following description is primarily concerned witha machine and process for extruding a multilayer film that includes ribson at least one layer.

Briefly, the machine 50 may include one or more dies, such as die 52,configured to receive a stream of molten plastic. The die 52 defines anannulus 54 through which the molten plastic is passed, or extruded. Theannulus 54 may be substantially circular in shape, but that is notrequired and annuluses 54 having other shapes may be employed. Where theannulus 54 is substantially circular in shape, the annulus 54 defines aninner diameter 56 having a size that can be selected depending upon therequirements of a particular application. In some instances, the innersurface 58 of the annulus 54 can be substantially smooth and free of anydiscontinuities or other geometric features, and the same may likewisebe true of the outer surface (this example not shown) of the annulus 54,although that is not necessary. In this example, the die 52 may producea film layer that has a substantially smooth outer surface.

In other instances however, the inner surface 58 of the annulus 54 maybe substantially smooth and free of any discontinuities or othergeometric features, while the outer surface 59 of the annulus 54 mayinclude one or more elements 60 configured and arranged such that as themolten plastic passes through the die 52, the outer surface of theextruded film layer assumes a structure and appearance that correspondswith the configuration and arrangement of the elements 60 of the outersurface 59. In the example of FIG. 1, the elements 60 comprise grooveshaving a substantially U-shaped configuration, and the elements 60 aresubstantially evenly spaced about the outer surface 59 so that anextruded film produced by the die 52 includes a ribbed outer surfacehaving ribs extending, for example, in the machine direction, thoughribs oriented in other directions may also be produced. In general, theconfiguration of the ribbed outer surface will reflect the size, number,shape, and spacing of the elements 60. Where the elements 60 comprisegrooves, the grooves may have sharp or rounded bottoms and can all besubstantially the same size, or different sizes.

While the elements 60 in the example of FIG. 1 comprise grooves, theelements 60 can have any other desired structure. Accordingly, the scopeof the invention is not limited to ribbed, extruded films having anouter surface structure and appearance that corresponds to the exampledie 52 of FIG. 1. Further, while the example annulus 54 indicated inFIG. 1 includes a substantially smooth inner surface and a ribbed outersurface, it will be appreciated that various types of annuluses, orfunctionally comparable structures, can be employed to produce filmswith particular characteristics, and the scope of the invention is notlimited to films such as may be produced by the annulus 54. Toillustrate, an annulus may be employed that includes elements 60, suchas ribs for example, on both its inner and outer surfaces, so as toproduce a film that is ribbed on both sides. As another example, anannulus may be employed that includes elements 60 on its inner surface,but not on its outer surface, so as to produce a film with an outersurface that is relatively smooth and an inner surface that includesfeatures produced by elements 60, such as ribs for example.

With reference now to FIGS. 2 a and 2 b, details are provided concerningaspects of a machine 150 that may be employed in the post-extrusionprocessing of a film, such as film 250 for example, to produce one ormore of the ribbed films disclosed herein.

With regard initially to a film, the example film 250 may be anextruded, multilayer precursor film and may comprise any of thematerials disclosed herein. For example, the film 250 may comprise twoor more layers, such as a core layer positioned between two skin layers.Such a film 250 may be formed in whole or in part, by extrusion, forexample. Moreover, at least one of the skin layers may include ribs 251formed by the extrusion process, that is, extruded ribs. As indicated inFIG. 2 a, the ribs 251 may extend generally parallel to the machinedirection, but that is not required. A film 250 that has not beensubjected to post-extrusion processing, and which has at least one layerthat includes such ribs 251, may be referred to herein as a ribbedprecursor film.

In any case, the film 250 can have an initial thickness or startinggauge 252 defined by the distances between its top 254 and bottomsurfaces 256. In at least one embodiment, the starting gauge 252, aswell as the respective gauges of the individual layers can besubstantially uniform along the length of the film 250.

With regard now to the machine 150, FIGS. 2 a and 2 b disclose portionsof a machine 150 that can implement an MD ring rolling process that mayimpart indicia to the film 250 and/or cause the appearance of indicia onthe film 250. It should be noted that an MD ring rolling process is oneparticular example of an MD stretching process. Other processes besidesMD ring rolling can be used to effect MD stretching. As discussed infurther detail below, such indicia may include, for example, stars,dots, discontinuities, stitches, and any other physical and/or visualindicia that may result from the MD processing of the film 250. Morespecifically, such indicia may include indicia that results from thephysical contact between the MD machine and/or other post-extrusionprocessing machines and portions of the film 250, such as the ribs 251,and such indicia may additionally, or alternatively, include color,intensified color, and other effects that result from the stretching ofthe film 250, such as by the machine 150.

In the example of FIGS. 2 a and 2 b, the machine 150 includes a pair ofMD intermeshing rollers 152 and 154 through which the film 250 ispassed. As a result of MD ring rolling, the film 250 is intermittentlystretched in the machine direction MD, and/or portions of the film 250such as the ribs 251 for example, may be subjected to stress and/orstrain due to physical contact between those portions of the film 250and machine 150 elements such as the rollers 152 and/or 154.

With regard to their configuration, FIG. 2 a discloses that the firstroller 152 and the second roller 154 can each have a generallycylindrical shape, and are operable to rotate in opposite directionsabout respective parallel axes of rotation 152 a and 154 a that may begenerally parallel to the transverse direction TD and generallyperpendicular to the machine direction MD. The rollers 152 and 154 eachinclude a respective plurality of radially protruding ridges 156 and 158that extend along the respective rollers 152 and 154 in a directiongenerally parallel to the axes of rotation 152 a and 154 a. Therespective tips 156 a and 158 a of ridges 156 and 158 can have a varietyof different shapes and configurations, including the rounded shape asshown in FIG. 2 b. In alternative implementations, the tips 156 a and158 a of the ridges 156 and 158 can have sharp angled corners. Asfurther indicated in FIGS. 2 a and 2 b, the ridges 156 are separated bygrooves 160, while the ridges 158 are separated by grooves 162.

The ridges 156 and 158 are staggered relative to each other so that thegrooves 160 can receive at least a portion of the ridges 158 as therollers 152 and 154 intermesh with each other. Correspondingly, thegrooves 162 can receive at least a portion of the ridges 156. In atleast some instances, the configuration of the ridges 156 and 158 andgrooves 160 and 162 can prevent substantial contact between ridges 156and 158 during intermeshing such that little or no rotational torque istransmitted during operation. Additionally, the configuration of theridges 156 and 158, and of the grooves 160 and 162 can affect the amountof stretching of the film 250 as it passes through the rollers 152 and154.

With continued reference to FIGS. 2 a and 2 b, the pitch and depth ofengagement of the ridges 156 and 158 can determine, at least in part,the amount of incremental stretching caused by the intermeshing rollers152 and 154. As shown in FIG. 2 b, the pitch 164 is the distance betweenthe tips of two adjacent ridges on the same roller. The depth ofengagement (DOE) 166 is the amount of overlap between adjacent ridges156 and 158 of the rollers 152 and 154 during intermeshing.

As is evident from the foregoing, various parameters of the machine 150may be selected and implemented depending upon the effect(s) desired tobe achieved. For example, the ridge pitch and/or DOE may be varied asnecessary. Merely because these parameters, and others, may be variedhowever, such variations will not necessarily be evident to one ofordinary skill in the art, and may, in some instances at least, bearrived at only after substantial experimentation and trials.

As indicated in FIGS. 2 a and 2 b, the direction of travel of the film250 through the intermeshing rollers 152 and 154 is generally parallelto the machine direction and generally perpendicular to the transversedirection. As the film 250 passes between the intermeshing rollers 152and 154, the ridges 156 and 158 incrementally stretch the film 250 inthe machine direction. In one or more implementations, stretching thefilm 250 in the machine direction can reduce the gauge of the film andincrease the length of the film 250. In other implementations, the film250 may rebound after stretching such that the gauge of the film 250 isnot substantially decreased. Furthermore, in one or moreimplementations, stretching the film 250 in the machine direction canreduce the width of the film 250. For example, as the film 250 islengthened in the machine direction, the width of the film 250 can bereduced in the transverse direction.

In particular, and as best shown in FIG. 2 b, as the film 250 proceedsbetween the intermeshing rollers 152 and 154, the ridges 156 of thefirst roller 152 can push film 250 into the grooves 162 of the secondroller 154, and the ridges 158 of the second roller 154 can also pushthe film 250 into the grooves 160 of the first roller 152. The pullingof the film 250 by the ridges 156 and 158 can stretch the film 250.However, the rollers 152 and 154 need not necessarily stretch the film250 evenly along its length. Specifically, the rollers 152 and 154 canstretch the portions of the film 250 between the ridges 156 and 158 morethan the portions of the film 250 that contact the ridges 156 and 158,as indicated in FIG. 2 b.

Thus, the rollers 152 and 154 can cooperate to form a series of machinedripples 258 in the film 250 such that the film 250 includes relativelythicker portions alternating with relatively thinner portions. Asindicated in FIG. 2 a, the ripples 258 in this particular example aredisposed generally parallel to the transverse direction. In this examplethen, the ripples 258 are generally orthogonal to the ribs 251, but suchan arrangement is not required. Thus, the finished film 250 may be arippled film of multi-layer, or single layer, construction. As disclosedelsewhere herein, various desirable visual effects and characteristicsmay be achieved through selection and processing of various films thatmake up a multi-layer implementation of the film 250.

Directing attention now to FIG. 2 c, and with continuing attention toFIGS. 2 a and 2 b, details are provided concerning aspects of an examplemachine and process which may be useful in creating various indicia on afilm layer, such as a ribbed film layer for example. In particular, itcan be seen that when an MD ring rolling process, for example, isperformed on the example film 250 (see FIGS. 2 a and 2 b), the ridges156 and 158 may temporarily or permanently compress portions of the ribs251. The compressions 260 may, but need not, be generally orthogonal tothe direction of the ribs 251.

It will be appreciated that the compressions 260 of the ribs 251constitute one example of indicia, discussed in more detail elsewhereherein. The color, size, number, geometry and orientation of thecompressions 260 may depend on one or more of the particular ringrolling process performed, roller pitch, DOE, material(s) of the film,and coloring agents such as pigments and/or voiding agents present inone or more film layers.

MD ring rolling is one example of method suitable to impart indicia to afilm, such as a multi-layer film for example, by incremental stretchingof the film in the machine direction. TD ring rolling is anothersuitable method of imparting indicia to a film such as a multi-layerfilm for example, by incremental stretching of the film in thetransverse direction. TD ring rolling, like MD ring rolling, may be usedalone or in conjunction with other processes. While not specificallyillustrated, a TD ring rolling machine and associated process may besimilar, respectively, to the MD ring rolling machine and associatedprocess, though the rollers of a TD ring rolling machine include ridgesand grooves that extend generally parallel to the MD direction, ratherthan orthogonal to the MD direction, as in the case of an MD machine andprocess. Thus, a TD ring rolling process may produce a rippled filmhaving ripples that are generally parallel to the MD direction. Similarto the case of MD ring rolling, it should be noted that a TD ringrolling process is one particular example of a TD stretching process.Other processes besides TD ring rolling can be used to effect TDstretching.

Finally, FIG. 2 d discloses some example cross-sectional element 60 a,60 b and 60 c shapes, such as rib shapes, and element combinations 60 d,60 e, 60 f and 60 g which can be employed on the inner and/or outerlayers of a film. As indicated in FIG. 2 d, where the elements areemployed on inner and outer layers, the elements on opposing sides ofthe film can be substantially aligned with each other, or staggeredrelative to each other. It should be noted that the scope of theinvention is not limited to those shapes. Moreover, different sizes andconfigurations of ribs can be combined in a single film.

E. Example Processes for Creating Films

It was noted earlier that formation of embodiments of the invention mayinclude the use of an extrusion process. Directing attention now to FIG.3, details are provided concerning an example process 300 that may beemployed in the production of films, such as the example films notedherein. It should be noted that while FIG. 3 refers to the use ofvoiding agents, any suitable type of coloring agent may alternatively beemployed in connection with one or more of the processes set forth inthat Figure.

E.1 Coextrusion

The example process 300 begins at 302 where a core layer resin and askin layer resin are prepared. This may involve preparing blends for theskin and/or core layers in preparation for an extrusion process. In atleast some embodiments, a skin layer blend is prepared that will be usedfor one or more skin layers. The blend may comprise LLDPE or any otherplastic material(s) disclosed herein.

At 304, a voiding agent is added to at least one of the skin layer blendand the core layer blend. In some embodiments, the voiding agent(s)is/are added only to the skin layer resin. The voiding agent may beadded prior to, during, or after, melting of the layer resin. Thevoiding agent may be in various forms, examples of which include drypowder form, and solution. As discussed in more detail below, thevoiding agent may be colorless, translucent, white, or any other color.In at least some cases, the voiding agent may comprise calcium carbonate(CaCO₃). However, as noted elsewhere herein, other suitable voidingagent(s), and combinations thereof, can alternatively be employed.

In a least some instances, calcium carbonate is but one example, thevoiding agent may be stress-sensitive. As such, the voiding agent mayappear to be substantially colorless in, for example, an un-stretched,or otherwise unstressed, film. However, stress and/or strain imposed onthe film including the coloring agent may cause film elements, such asribs for example, that include the voiding agent to change color. One ormore examples of such a film are disclosed elsewhere herein. In otherinstances, a voiding agent itself may be colorless or substantially so,but stress or strain applied to voids created by a voiding agent maycause the resin in the vicinity of the voids to change color.

After the voiding agent has been added to the blend, the process 300moves to 306 where the skin layer resin and core layer resin arecoextruded to form an extruded multilayer film. As noted elsewhereherein, at least some embodiments provide for the use of a die thatincludes elements which cause the formation of ribs on the skin layer asthe skin layer resin is extruded through the die.

After coextrusion 306, the resulting extruded multilayer film may besubjected to various types of post-extrusion processing 308. In someinstances, such as in the example of FIG. 3, the post-extrusionprocessing takes place prior to lamination of the extruded multilayerfilm with any other films. In other instances, the post-extrusionprocessing is performed during, or after, the lamination of the extrudedmultilayer film with one or more other films. More generally, one ormore post-extrusion processes may be performed at any, or all, of theaforementioned junctures. Accordingly, the scope of the invention is notlimited to any particular post-extrusion process, or combination ofprocesses, nor is the scope of the invention limited to performance ofthe post-extrusion processes at any particular juncture(s) afterformation of the extruded multilayer film.

With continued reference to FIG. 3, the post-extrusion processing mayinclude stretching, examples of which include one or more of MD ringrolling and TD ring rolling, performed in any order. In some exampleembodiments, the MD ring rolling is performed prior to the TD ringrolling, but that is not necessary. In yet other example embodiments,only MD ring rolling is performed. More generally, one or morepost-extrusion processes may comprise incremental stretching or otherplastic and/or elastic deformation of the extruded, ribbed multilayerfilm in one or more directions simultaneously, or serially.

As disclosed elsewhere herein, the post-extrusion processing of theextruded, ribbed multilayer film may result in the formation of varioustypes of indicia in and/or on the ribbed skin layer and/or elsewhere inthe extruded, ribbed multilayer film.

E.2 Voiding Agents

As noted earlier, at least some of the processes that may be employed tocreate the films disclosed herein generally involve the coextrusion oftwo or more film layers to form a coextruded multilayer film. Consistentwith the embodiments disclosed herein, one or more coloring agents, suchas voiding agents for example, may be added to one or more film resinsprior to coextrusion of a multilayer film. In general, voiding agentsinclude, among other things, any material, or combination of materials,that serve to create, or facilitate the creation of, voids in a resin orother material in which the voiding agent is dispersed. Thus, a film inwhich a voiding agent has been dispersed may include voids disposed,uniformly or otherwise, throughout the film. The presence andconcentration of such voids can have a variety of effects on theappearance of the associated film.

For example, relatively thicker portions of the film may includerelatively more voids than thinner portions of the film. Thus, thethicker portions of the film may contrast visibly in terms of colorand/or color intensity with the thinner portions of the film. As anotherexample, thicker and thinner portions of the film may react differentlyto the imposition of stresses. This can be due to the relativelydifferent physical structures of those portions, namely, the thickerportion includes more voids than the thinner portion, such thatimposition of stress may, as noted in some examples herein, causethicker portions such as ribs to change color and/or to become moreintense in color, while thinner portions may be less affected in termsof their color and/or color intensity. Thus, a voiding agent introducedinto a material can cause one or more colors to be imparted to thatmaterial, by various mechanisms, notwithstanding that the voiding agentitself may have little or no intrinsic color. In other instances, avoiding agent may have an intrinsic color that may affect the appearanceof a film into which the voiding agent is introduced.

Some examples of voiding agents that may be employed in connection withvarious embodiments of the invention include, but are not limited to,calcium carbonate, magnesium carbonate, barium carbonate, calciumsulfate, magnesium sulfate, barium sulfate, calcium oxide, magnesiumoxide, titanium oxide, zinc oxide, aluminum hydroxide, magnesiumhydroxide, talc, clay, silica, alumina, mica, glass powder, starch, andany combination of the foregoing. Organic voiding agents, one example ofwhich is polystyrene, may also be used in connection with variousembodiments of the invention. At least some of these voiding agents,such as calcium carbonate for example, may have an intrinsic color, suchas white, that will be manifest in a film that employs the voidingagent.

It was noted earlier that in one particular example, a suitable voidingagent comprises calcium carbonate. In general, the concentration of thevoiding agent can be varied depending, for example, upon variables suchas the layer in which a masterbatch is to be used, the material of thelayer in which the voiding agent or masterbatch is to be employed, acolor and/or concentration of the masterbatch, and the presence, or not,of other coloring agents in the resins that are used to form the otherlayers of an extruded multilayer film. Accordingly, the scope of theinvention is not limited to any particular concentration, or range(s) ofconcentration, of the voiding agent.

In one specific example however, a calcium carbonate voiding agentconcentration in a range of about 5 percent to about 25 percent has beenfound useful in some embodiments of a skin layer. Further, aconcentration of the calcium carbonate voiding agent of about 15 percenthas been found to be particularly useful in some embodiments of the skinlayer.

Finally, it should be noted that in certain circumstances, theconcentration of the voiding agent in a layer may be a function of ribthickness, or the thickness of other elements of a layer or film, suchthat relatively thicker ribs may permit the user of a relatively lowerconcentration of voiding agent. This may be advantageous inasmuch asrelatively thicker ribs may enable an overall reduction in cost byreducing the amount of voiding agent required. Further, relativelythicker ribs contribute to an overall increase of a layer and film inwhich the ribs are employed. Correspondingly, excessive voiding agentconcentrations can negatively affect the structural integrity of a film.Thus, the need for the useful effects that a voiding agent can providemay need to be balanced with negative effects that may attend excessiveconcentrations of the voiding agent.

F. Example Films

In general, and within the scope of this disclosure, there are a varietyof films that may be produced and, accordingly, it should be understoodthat the embodiments of films set forth in the Figures, and discussedherein, are presented solely by way of illustration and are not intendedto limit the scope of the invention in any way. The example filmsdiscussed below are extruded, ribbed films that may be produced in avariety of different ways, including the example extrusion, and other,processes noted above.

In addition to a visually appealing appearance, such ribs may provide astructure that deforms, thereby producing indicia, when subjected tovarious ring rolling (RR) processes, such as DD, MD, and/or TD ringrolling. As noted elsewhere herein, variables such as pitch of ribs,DOE, and/or RR teeth can be adjusted to provide desirable visual effectsin the film.

F.1 Example Film ‘A’

FIGS. 4 a-1 through 4 d-2 and the corresponding text provide detailsconcerning an example ribbed film laminate structure referred to hereinas Film ‘A.’ In this particular example, Film ‘A’ is an extruded filmthat comprises three layers of linear low-density polyethylene (LLDPE),having a layer structure of A:B:A, wherein the layer ratio for the threelayers is about 20:60:20. That is, the outer two layers, or skin layers,each have a thickness of about 20 percent of the total thickness of Film‘A’, while the core layer has a thickness of about 60 percent of thetotal thickness of Film ‘A’.

FIGS. 4 a-1 through 4 d-2 further show that both the core layer and theskin layers are un-pigmented. In FIGS. 4 a-1, 4 b-1, 4 c-1 and 4 d-1,the left-side portion of the film is shown on a white background, andthe right-side portion of the film is shown on a black background, tobetter disclose various aspects of the film. The same is likewise trueof FIGS. 5 a-1, 5 b-1, 5 c-1, 6 a-1, 6 b-1 and 6 c-1. In FIGS. 7 a-1, 7b-1 and 7 c-1, only a black background is used.

The ribs of Film ‘A’ averaged about 6.5 mils tall, with an averagespacing between extruded ribs 403 of about 0.336 inches. The thicknessof the web 405 between consecutive extruded ribs 403 was targeted to beabout 0.50 mils thick. As indicated in the Figures, the extruded ribs403 appear translucent as a result of their relative thickness, and as aresult of its thinness, the web 405 between the extruded ribs 403appears to be nearly colorless.

With particular reference first to FIGS. 4 a-1 and 4 a-2, an embodimentof Film ‘A’ is disclosed that reflects an absence of post-extrusionprocessing, such as MD or TD ring rolling. As illustrated, the ribs 403have a hazy appearance, and the web 405 between the ribs 403 is largelytranslucent.

FIGS. 4 b-1, 4 b-2, 4 c-1 and 4 c-2 further disclose that differenteffects can be achieved in, for example, the appearance and/or feel of aribbed film by varying the post-extrusion tools and/or processingemployed in connection with the film. Such tools and/or processing caninclude one or more of DOE, tooth pitch, tooth shape, and ring rollingincluding one or more of TD, MD and DD ring rolling. To illustrate,FIGS. 4 b-1, 4 b-2, 4 c-1 and 4 c-2 disclose an implementation in whichFilm ‘A’ was stretched by an MD process using a 200 pitch tool and a DOEof about 150 mils. MD stretching with these parameters resulted in theweb 405 having a hazier appearance, relative to the un-stretchedembodiment of FIGS. 4 a-1 and 4 a-2, while the ribs 403 experienced nosubstantial change in color or haze. This is particularly apparent whenreferring to the right hand side of FIGS. 4 a-1 and 4 b-1, where Film‘A’ is disposed on a black background. In FIG. 4 c-1, in particular, itcan be seen that the MD stretching produced a number dots or stars 407in the ribs 403.

FIGS. 4 d-1 and 4 d-2 disclose the embodiment of FIGS. 4 b-1, 4 b-2, 4c-1 and 4 c-2 after that embodiment was further subjected to a TD ringrolling process with a 40 pitch tool and DOE of about 20 mils. Theadditional TD ring rolling process produced no substantial change in thehaze of the web 405 between the ribs 403. Similarly, this processproduced no substantial color change in the extruded ribs 403 or web 405between the extruded ribs 403.

F.2 Example Film ‘B’

FIGS. 5 a-1 and 5 a-2 discloses aspect of another film referred toherein as Film ‘B,’ before any ring rolling, such as TD or MD ringrolling, has been performed. Similar to Film ‘A,’ Film ‘B’ is anextruded, ribbed film laminate structure that comprises three layers oflinear low-density polyethylene (LLDPE) having a layer structure ofA:B:A, where the layer ratio for the three layers is about 20:60:20.

In this example, the core layer (or ‘B’ layer of the A:B:A structure) isun-pigmented, but in contrast with Film ‘A,’ the skin layers containabout 20 percent calcium carbonate (CaCO₃) masterbatch, a voiding agent.As in the case of Film ‘A’, the ribs 503 of Film ‘B’ average about 6.5mils tall, with an average spacing between ribs 503 of about 0.336inches. The thickness of the web 505 between the ribs 503 was targetedto be about 0.50 mils thick. The example of FIG. 4 a indicates that,absent any ring rolling, the ribs 503 of Film ‘B’ have a hazytranslucent appearance due to the presence of the CaCO₃ and thethickness of the ribs 503, while the web 505 between the ribs 503 washazy but nearly colorless.

FIG. 5 b indicates the effect on Film ‘B’ of the performance of an MDring rolling process. In particular, FIGS. 5 b-1 and 5 b-2 illustratethe effect on Film ‘B’ after application of an MD ring rolling processusing a 200 pitch tool and a DOE of about 150 mils. As shown in thoseFigures, MD ring rolling and consequent stretching of Film ‘B’ underthese parameters resulted in a relatively hazier appearance of the web505 between the ribs 503, while the ribs 503 took on a visibly enhancedwhite color. FIGS. 5 b-1 and 5 b-2 further show that the ribs 503 eachcomprise a white “stitch” 507 or cross pattern that intermittentlycrosses each rib 503. This is particularly apparent when referring tothe right hand side of FIG. 5 b, where Film ‘B’ is disposed on a blackbackground. The “stitch” patterns are areas in which the MD rollersstress that particular area of the rib 503, causing the voiding agent,which is stress-sensitive, to react and produce areas of enhancedwhiteness along the ribs 503. As in the case of Film ‘A’ in FIGS. 4 a-1through 4 d-2, however, the stretching resulting from the TD ringrolling process has no such effect on the MD ring rolled Film ‘B.’ Asdiscussed in more detail below, the aforementioned stitches are oneexample of indicia that may be produced in connection with variousembodiments.

Notably, FIGS. 5 c-1 and 5 c-2 illustrate Film ‘B’ after theapplication, to the film of FIGS. 5 b-1 and 5 b-2, of a TD process usinga 40 pitch tool and a DOE of about 20 mils. As indicated, that TDprocess produced no significant change in the ribs 503, or in web 505.

F.3 Example Film ‘C’

FIGS. 6 a-1 through 6 c-2 provide details concerning another exampleribbed film, referred to herein as Film ‘C.’ In this particular example,Film ‘C’ is an extruded ribbed film that comprises three layers oflinear low-density polyethylene (LLDPE), having a layer structure ofA:B:A, wherein the layer ratio for the three layers is about 20:60:20.As in the case of Films ‘A’ and ‘B,’ discussed above in connection withFIGS. 4 a-1 through 5 c-2, the ribs 603 of Film ‘C’ average about 6.5mils tall, with an average spacing between ribs 603 of about 0.336inches. The thickness of the web 605 between the ribs 603 was targetedto be about 0.50 mils thick.

In contrast with Film ‘B,’ however, Film ‘C’ comprises a black coloringagent that causes the ribs 603 to appear black. Specifically, Film ‘C’comprises a core layer (layer B of layer structure A:B:A) that wasun-pigmented, albeit with skin layers (layers A of structure A:B:A) thatcontained a dilute pigment, about 0.5 percent black masterbatch in thisexample. By way of explanation, Applicants have found that a dilutepigment having a concentration in the range of about 0.25 percent toabout 3.0 percent may provide acceptable results in this and/or otherembodiments. Applicants have also found that concentrations in a rangeof about 0.25 percent to about 2.0 percent may be useful in someinstances, and concentrations in a range of about 0.25 percent to about1.0 may be particularly useful in some instances.

With particular reference to FIGS. 6 a-1 and 6 a-2, which disclose anun-stretched version of Film ‘C,’ the ribs 603 appear black due to theirthickness and the presence of the black masterbatch. Due to its relativethinness, the web 605 between the ribs 603 can appear to be nearlycolorless to slightly hazy.

FIGS. 6 b-1 and 6 b-2, however, show the effects of applying an MDstretching process, to the film of FIGS. 6 a-1 and 6 a-2, where the ribs603 are colored, but otherwise comprise no voiding agents that mightchange or enhance color with stress. The MD ring rolling was performedusing a 200 pitch tool and a DOE of about 150 mils. Specifically, FIGS.6 b-1 and 6 b-2 show that applying MD stretching under these parameterscan produce some intermittent deformation 607 of the film at uniformpoints along the ribs 603, and a corresponding hazier appearance of theribs 603, but otherwise produce no color change to the ribs 603.Similarly, the web 605 can become hazier as well, but otherwise undergono color change. The additional application, to the film of FIGS. 6 b-1and 6 b-2, of a TD process using a 40 pitch tool and a DOE of about 20mils produced no discernible change in the ribs 603 or intervening film605, as indicated in FIGS. 6 c-1 and 6 c-2. As discussed in more detailbelow, the aforementioned intermittent deformation of the ribs 603 isanother example of indicia that may be produced in connection withvarious embodiments.

F.4 Example Film ‘H’

FIGS. 7 a-1 through 7 c-2 and the corresponding text provide detailsconcerning an example ribbed film referred to herein as Film ‘H.’ Asindicated in those figures, Film ‘H’ is a ribbed film. In thisparticular example, Film ‘H’ is an extruded film that comprises threelayers of linear low-density polyethylene (LLDPE). In this example, Film‘H’ has a layer structure of A:B:A. The layer ratio for the three layersis about 20:60:20.

In this example, the core layer comprised about 6 percent blackmasterbatch, and the skin layers contained about 20 percent CaCO₃masterbatch. The ribs 703 of Film ‘H’averaged about 6.5 mils tall, withan average spacing between ribs 703 of about 0.336 inches. The thicknessof the intervening film 705 between the ribs 703 was targeted to beabout 0.50 mils thick.

Observation of Film ‘H’ in FIGS. 7 a-1 and 7 a-2 reveals hazy, graycolored ribs, and black film between the ribs. The sample of FIGS. 7 a-1and 7 a-2 was not subjected to any post-extrusion processing. In thesample of FIGS. 7 a-1 and 7 b-2, which reflects application of an MDstretching process with a 200 pitch tool at a DOE of about 150 mils, theribs 703 have a white, stitched 707 appearance, and the black web 705between the ribs 703 remains black. As indicated in FIGS. 7 c-1 and 7c-2, a TD stretching process, with a 40 pitch tool at about 20 mils DOE,performed subsequent to the MD stretching process resulted in no colorchange to the ribs 703 or to the web 705 between the ribs 703, ascompared with the film of FIGS. 7 b-1 and 7 b-2.

G. Examples of Post-Extrusion Processes and Resulting Indicia

As will be apparent from the foregoing discussion and example films andstructures, various processes may be employed to provide indicia thatmay convey information to a user concerning an end product in which thefilm and/or structure is employed.

In connection with the processes disclosed herein, including those setforth in the discussion of FIG. 3 above, various physical indicators mayresult from the performance of those processes and/or may be present inprecursor films used in such processes. Consistent with the foregoing,and as set forth in the discussion of the structures below, such indiciamay include, for example, elements such as colors, dyes, pigments,textures, ribs, corrugations, stars, dots, bars, stitches, discontinuouslines, and combinations of any of the foregoing. Not only are suchindicia readily apparent to a user of, for example, an end product inwhich the discontinuously laminated film structure is employed, but suchindicia may be advantageous insofar as they are perceptible by one ormore senses of a user.

The indicia may be formed at various different times during theproduction process. For example, the indicia may be formed bypost-extrusion processing of an extruded multilayer film. As anotherexample, the indicia may be formed as part of a discontinuous laminationprocess in which an extruded multilayer film is discontinuouslylaminated to one or more other layers. As a further example, indicia maybe formed both during post-extrusion processing of an extrudedmultilayer film, and also during a discontinuous lamination process inwhich that same extruded multilayer film is discontinuously laminated toone or more other layers.

Various types of indicia may be present in a particular end product,discontinuously laminated film structure, or precursor film. Forexample, one type of indicia may convey to a user information concerningan attribute of an end product. Another type of indicia may serve alargely cosmetic or aesthetic purpose. The foregoing and/or other typesof indicia may be combined, for example, in a single end product.

By way of illustration, indicia may indicate visually, and/or in atactile sense, certain attributes of the end product such as, forexample, a relative strength of the product. Thus, the extruded ribspresent in a precursor film enhance the strength of the precursor film.As well, such extruded ribs also provide a visible and tactileindicator, to a user, of the strength of the film and/or the strength ofa discontinuously laminated film structure or end product in which thatfilm is employed.

As another example, the stars or dots present in some of the‘Structures’ noted below serve as an indicator of highly localizedstress whitening, such as may be obtained with various combinations ofring rolling processes, such as MD and/or TD ring rolling. The highlylocalized stress whitening, which may result from ring rolling in adirection generally orthogonal to a direction of extruded ribs of afilm, can serve as an indicator to a consumer as to the strength of thediscontinuously laminated film structure, since the localized stresswhitening occurs at points where the extruded ribs are worked by theteeth of a roller.

Moreover, the formation of indicia such as localized stress whiteningcan be localized and controlled using various combinations of voidingagents, and coloring agents such as dyes, dilute pigments, variousprocesses such as cold MD and/or TD ring rolling. Indeed, such whiteningcan be highly localized, if desired, as evidenced by indicia such as thedots and stars disclosed elsewhere herein. More generally,stress-sensitive coloring agents such as certain dyes and pigments, andstress-sensitive voiding agents can be employed in one or more layers ofa discontinuously laminated film structure such that formation of thelayers and/or the discontinuously laminated film structure causes achange to the element(s) that include the coloring agent, therebyproviding a visible manifestation of induced stress and/or strain.

As noted above, some indicia within the scope of this disclosure may belargely cosmetic or aesthetic in nature. For example, MD ring rolling ofthe extruded ribs in a ribbed precursor film provides an interestingvisual effect that may have little to do with the strength or integrityof the precursor film or associated discontinuously laminated filmstructure.

Finally, and with regard to the foregoing discussion, it will beapparent that insofar as indicia convey to a user information concerninga property of a precursor film, discontinuously laminated filmstructure, and/or end product, such indicia are example implementationsof means for conveying information perceptible by one or more senses ofa user. Thus, the indicia disclosed herein are provided solely by way ofexample, and any other indicia of comparable functionality mayalternatively be employed.

In light of the disclosure herein, it will be appreciated thatembodiments of the invention may be advantageous in various waysrelative to conventional structures and processes. Below are set forthvarious examples of some advantages that may be achieved in connectionwith one or more embodiments of the invention. It is not necessary thatall of such examples be present in any particular embodiment, nor is itnecessary that any particular example be present in an embodiment.Finally, it should be noted that the examples set forth below areprovided solely by way of illustration and are not intended, nor shouldbe construed, to limit the scope of the invention in any way.

H. Example Advantages of Some Embodiments

With regard now to some possible advantages of example embodiments, oneor more embodiments of the invention may substantially maintain theircolor characteristics, notwithstanding temporary or permanentdeformation of the film. As another example, one or more embodiments ofthe invention may implement various visual effects, such as coloration,with non-metallic films. As a further example, one or more embodimentsof the invention may implement various visual effects such as colorationwithout the use of color-generating laminates or layers. As yet anotherexample, one or more embodiments of the invention may provide visualeffects such as coloration without requiring user manipulation, such asby bending or delamination for example, with regard to the finishedfilm. Moreover, one or more embodiments of the invention may implementdesired visual effects with discontinuously laminated films, and thus donot require intimate contact between film layers. As well, one or moreembodiments of the invention may implement desired visual effects withfilm structures that include at least one ribbed film. Further, one ormore embodiments of the invention may realize a relative increase instrength as a result of MD rolling and/or TD rolling of a ribbedprecursor film or a laminated film that includes such a rolled precursorfilm. Moreover, the relative strength of the film and/or of a productthat employs the film may be visually indicated to a user by indiciasuch as a color, contrasting colors, and/or distribution of the color inthe film or product. As another example, the incremental stretchingprocesses disclosed herein, such as TD and MD ring rolling for example,may be advantageous over conventional continuous-stretch processes thatdo not produce indicia and the other effects noted herein. As a finalexample, one or more of the embodiments disclosed herein may beadvantageous inasmuch as they possess, or produce, as applicable,indicia using a continuous process. More conventional processes, such asstamping or embossing, are not well suited to be implemented in acontinuous fashion. Rather, only discrete portions of the film can bestamped or embossed.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, theillustrated and described implementations involve non-continuous (i.e.,discontinuous or partially discontinuous lamination) to provide thelight bonds. In alternative implementations, the lamination may becontinuous. For example, multi film layers could be co-extruded so thatthe layers have a bond strength that provides for delamination prior tofilm failure to provide similar benefits to those described above. Thus,the described embodiments are to be considered in all respects only asillustrative and not restrictive. All changes that come within themeaning and range of equivalency of the claims are to be embraced withintheir scope.

What is claimed is:
 1. A film, comprising: a coextruded structure that includes: a ribbed skin layer that includes a plurality of ribs, where consecutive ribs are spaced apart from each other by a web that is integral with the consecutive ribs; and a core layer attached to the ribbed skin layer; and a voiding agent, wherein the voiding agent is present in the ribbed skin layer.
 2. The film as recited in claim 1, wherein the ribbed skin layer and the core layer both comprise plastic.
 3. The film as recited in claim 1, wherein the voiding agent is present only in the ribbed skin layer.
 4. The film as recited in claim 3, wherein the voiding agent is apparent substantially only in the ribs of the ribbed skin layer.
 5. The film as recited in claim 1, wherein the voiding agent is one of substantially opaque; translucent; and, transparent.
 6. The film as recited in claim 5, wherein the film further comprises a coloring agent in the core layer.
 7. The film as recited in claim 6, wherein the coloring agent is a different color than the voiding agent.
 8. The film as recited in claim 1, wherein there is a visible contrast between the ribs and the webs, and the visible contrast is at least one of: a contrast in color; and, a contrast in intensity of color.
 9. The film as recited in claim 1, wherein the voiding agent comprises, in any combination, one or more of: calcium carbonate; magnesium carbonate; barium carbonate; calcium sulfate; magnesium sulfate; barium sulfate; calcium oxide; magnesium oxide; titanium oxide; zinc oxide; aluminum hydroxide; magnesium hydroxide; talc; clay; silica, alumina; mica; glass powder; and, starch.
 10. The film as recited in claim 1, wherein the ribbed skin layer includes indicia perceptible by one or more senses of a user, and wherein the indicia are one of: substantially cosmetic in nature; and indicative of a physical property of the film.
 11. The film as recited in claim 10, wherein the indicia comprise one or more of: corrugations; ribs and webs of contrasting respective colors; substantially white ribs; substantially black ribs; discontinuities in the ribs that have the same color as the ribs; discontinuities in the ribs that have a different color than the ribs; and, haziness in the webs.
 12. The film as recited in claim 1, wherein the ribbed skin layer includes indicia perceptible by one or more senses of a user, and wherein the indicia are indicative of post-extrusion processing of the film, and the post-extrusion processing comprises one or more of MD stretching, MD ring rolling, TD stretching, and TD ring rolling.
 13. The film as recited in claim 12, wherein the indicia comprise one or more of: corrugations; ribs and webs of contrasting respective colors; substantially white ribs; substantially black ribs; discontinuities in the ribs that have the same color as the ribs; discontinuities in the ribs that have a different color than the ribs; and, haziness in the webs.
 14. A plastic product at least partly constructed from the film of claim 1, wherein the plastic product comprises one of a grocery bag, a trash bag, a sack, a yard waste bag, packaging materials, a feminine hygiene product, a baby diaper, and adult incontinence product, a sanitary napkin, a bandage, a food storage bag, a food storage container, a thermal heat wrap, a facial mask, a cleaning wipe, and a hard surface cleaner.
 15. A method for producing a film, comprising: adding a voiding agent to a skin layer resin; coextruding a core layer resin and the skin layer resin to form an extruded multilayer film having a plurality of ribs in the skin layer, where consecutive ribs are separated from each other by a web that is integral with the ribs; and performing post-extrusion processing on the extruded multilayer film, wherein the post-extrusion processing includes one or more of MD stretching, MD ring rolling, TD stretching and TD ring rolling.
 16. The method as recited in claim 15, wherein the voiding agent is substantially more apparent in the ribs of the skin layer than in the webs.
 17. The method as recited in claim 15, wherein the voiding agent is stress-sensitive.
 18. The method as recited in claim 15, further comprising adding a coloring agent to the core layer, the coloring agent having a different color than the voiding agent.
 19. The method as recited in claim 15, wherein MD ring rolling is performed on the extruded multilayer film, and the MD ring rolling causes the ribs to change one or both of: color; and, color intensity.
 20. The method as recited in claim 15, wherein MD ring rolling is performed on the extruded multilayer film, and the MD ring rolling causes the formation of indicia in the skin layer, wherein: the indicia comprise one or more of corrugations, ribs and webs of contrasting respective colors, substantially white ribs, substantially black ribs, discontinuities in the ribs that have the same color as the ribs, discontinuities in the ribs that have a different color than the ribs, and haziness in the webs; and the indicia are one or both of: substantially cosmetic in nature; and indicative of a physical property of the film. 